The invention pertains to a chipbreaker for use in conjunction with a metal cutting insert, as well as the combination of the chipbreaker and the metalcutting insert
A cutting tool assembly for metal working (e.g., turning, milling and boring applications) typically comprises a shank, a head portion and one or more cutting inserts. The workpiece or cutting tool assembly is rotated in a chuck. The cutting insert contacts the workpiece and a part of the workpiece is generally removed as rolls, coils or stringers of metal. Sometimes, the roll or stringer of metal will not break so as to become very long, and possibly, become tangled together. Such a long coil is known in this art as a bird's nest. Unfortunately, this long tight curl, i.e., bird's nest, is in the work area and may become entangled with the chuck holding the work piece. The long tight coil may also become entangled with the lead screw on the lathe and cutting tool assembly. Such a long tight coil of metal if permitted to exist may decrease the useful life of the cutting tool assembly or damage the surface of the workpiece.
Further, for example, if the machine tool operator must stop the lathe and remove the coil or roll of metal from the vicinity of the workpiece and the cutting tool, there is a loss in production of the machine tool operator which results in an increase in the cost of production of the workpiece. If there is a long roll or coil of metal in the work area, the work area is less safe for the machine tool operator than if the metal removed from the workpiece is broken into small chips.
A side effect of breaking the coil of metal from the workpiece into smaller segments, i.e., chips, is a better finish on the completed workpiece since the metal coil does not work in between the cutting edge of the cutting insert and the workpiece.
Further, if the metal removed from the workpiece is one continuous coil or stringer, the metal is not useful for being recycled and melted in a furnace. For example, one barrel of broken ships from the metallic workpiece is equal in weight to about twenty to thirty barrels of unbroken chips. It is easier to bale one barrel of broken chips than it is to bale twenty to thirty barrels of unbroken chips. In a melting furnace the temperature is in the range of thirty-two hundred to thirty-three hundred degrees fahrenheit (3200.degree. F.-3300.degree. F.). If the chips are not baled, the chips burn and vaporize and the metal is lost. Therefore, it is necessary to bale the chips for efficient recycling.
It is very apparent that there are some significant advantages to breaking the long coil into smaller segments or chips. These advantages pertain to the overall efficiency of the performance of the cutting tool assembly, the quality of the surface finish of the workpiece, the safety of the operator, and the enhancement of the recycling of the chips.
Referring to the chipbreaker itself, there are two basic categories of chipbreakers. The first category pertains to a chipbreaker which is an integral part of the cutting insert. The second category pertains to a chipbreaker that is mechanically, but releasably, held on the top or rake face of the cutting insert. Both categories of chipbreakers function in basically the same fashion in that the metal coil is deflected from the cutting insert into the surface of the chipbreaker which causes the coil to curl back towards the workpiece. Curling of the coil causes it to work harden, and thus, break into a short segment (or chip) shortly after curling. The result is that a long coil of metal is not formed as a result of the metal removal process, but instead, shorter more manageable chips are formed from the metal removal process.
It can thus be appreciated that a chipbreaker, which functions to break the coil of metal into small segments (or chip), is an important feature of the overall metal removal process. By providing an effective chipbreaker, one lengthens the useful life of the cutting insert, enhances the productivity of the machine tool operator, makes the workplace safer for the operator, produces a better surface finish on the workpiece, and assists in the effective baling and subsequent melting of the metal removed from the workpiece.